RFID UHF stripline coupler
View Patent ↗A stripline coupler for a RFID system is provided. The coupler is configured to communicate with a targeted transponder from among a group of multiple adjacent transponders. The coupler may include a conductive strip, a terminating load, a dielectric material, a first ground plane, and a second ground plane. The conductive strip extends between the first and second ground planes and the dielectric material from an input end connected to a transceiver to a loaded end connected to the terminating load. The conductive strip may be configured to propagate electromagnetic fields concentrated in a near field region of the conductive strip in a direction generally perpendicular to the conductive strip to couple with a targeted transponder. The coupler may include an enclosure for directing the electromagnetic fields. The conductive strip may have a tapered or non-linear profile such as a modified bow-tie profile, an exponential profile, or a Klopfenstein profile.
1. A stripline coupler for a RFID enabled system having a transceiver, the coupler being adapted to couple a transceiver with a targeted transponder in a transponder encoding region from among a group of multiple adjacent transponders, the coupler comprising: a first ground plane and a second ground plane spaced apart from each other; at least one connection between the first ground plane and the second ground plane for connecting the first ground plane to the second ground plane; and a conductive strip being positioned at least partially between the first and second ground planes and configured to propagate a plurality of electromagnetic fields; wherein the first ground plane, the second ground plane, and the at least one connection promote propagation of the plurality of electromagnetic fields from a side of the conductive strip; and wherein the propagation of the plurality of electromagnetic fields from the side of the conductive strip is in a direction generally perpendicular to a length of the conductive strip and generally parallel to the first and second ground planes for coupling with the targeted transponder in the transponder encoding region.
2. The stripline coupler according to claim 1 further comprising a dielectric material positioned between the first ground plane and the second ground plane.
3. The stripline coupler according to claim 2 , wherein the dielectric material is from the group consisting of a ceramic, a plastic, and a combination of ceramic and plastic.
4. The stripline coupler according to claim 2 , wherein the dielectric material is air.
5. The stripline coupler according to claim 1 , wherein the coupler is a near field coupler and the plurality of electromagnetic fields are concentrated in a near field region of the conductive strip.
6. The stripline coupler according to claim 5 further comprising an input port for connecting the coupler to the transceiver and a terminating load defining an input impedance, wherein the input impedance is substantially equal to a source impedance of the transceiver and wherein the conductive strip extends from a first end connected to the input port and a second end connected to the terminating load, wherein the first end and second end define a length of the conductive strip.
7. The stripline coupler according to claim 6 , wherein the coupler is configured to operate within a band of frequencies and the conductive strip defines a width that remains substantially constant along the length of the conductive strip and the length of the conductive strip is substantially equal to a half wavelength of a center frequency of the band of frequencies.
8. The stripline coupler according to claim 6 , wherein the coupler is configured to operate within a band of frequencies and the conductive strip defines a width that varies along the length of the conductive strip and defines a tapered profile and the length of the conductive strip is less than a half wavelength of a center frequency of the band of frequencies.
9. The stripline coupler according to claim 8 , wherein the tapered profile is a modified bow-tie profile.
10. The stripline coupler according to claim 8 , wherein the tapered profile is selected from the group consisting of an exponential profile and a Klopfenstein profile.
11. The stripline coupler according to claim 6 , wherein the input port is adjacent to the first ground plane and is connected to the first end of the conductive strip by a connection extending from the first ground plane to the conductive strip and the terminating load is adjacent to the first ground plane and is connected to the second end of the conductive strip by a connection extending from the first ground plane to the conductive strip.
12. The stripline coupler according to claim 6 , wherein the conductive strip defines a characteristic impedance less than the input impedance.
13. The stripline coupler according to claim 12 , wherein the input impedance is substantially equal to 50 ohms.
14. The stripline coupler according to claim 1 further comprising a plurality of connections between the first ground plane and the second ground plane, wherein the connections extend substantially around the conductive strip and define one active side of the coupler free of connections and configured to promote the propagation of the electromagnetic fields from the active side for coupling with the targeted transponder.
15. An RFID system for selectively communicating with a targeted transponder from among a group of multiple adjacent transponders, the RFID system comprising: a transponder conveyance system adapted to transport at least one targeted transponder from a group of multiple adjacent transponders through a transponder encoding region along a predetermined path; and a coupler including a conductive strip, a first ground plane, and a second ground plane, wherein the conductive strip is positioned at least partially between the first and second ground planes and is configured to transmit and receive an electromagnetic field to and from the transponder encoding region for communicating with the targeted transponder; and wherein coupler includes a plurality of connections between the first ground plane and the second ground plane and the connections extend substantially around the conductive strip and define one active side of the coupler free of connections and configured to promote propagation of a plurality of electromagnetic fields from the active side in a direction generally perpendicular to the length of the conductive strip and generally parallel to the ground planes for coupling with the targeted transponder.
16. The RFID system according to claim 15 further including a transceiver configured to generate communication signals, wherein the transceiver is in electrical communication with the coupler.
17. The RFID system according to claim 16 , wherein the coupler further includes a dielectric material positioned between the first ground plane and the second ground plane.
18. The RFID system according to claim 17 , wherein the coupler is a near field coupler configured to create a plurality of electromagnetic fields concentrated in a near field region of the coupler.
19. The RFID system according to claim 8 , wherein the near field coupler further includes a terminating load, and the conductive strip extends from an input end connected to the transceiver to a loaded end connected to the terminating load and between a first side edge and a second side edge, wherein the input end and the loaded end define a length of the conductive strip and the first side edge and the second edge define a width the conductive strip, and the width of the conductive strip is generally perpendicular to the targeted transponder during coupling.
20. The RFID system according to claim 19 , wherein the terminating load is configured to match an input impedance of the near field coupler to a source impedance of the transceiver.
21. The RFID system according to claim 20 , wherein the conductive strip defines a characteristic impedance less than the load impedance and the load impedance is substantially equal to the source impedance.
22. The RFID system according to claim 21 , wherein the coupler is configured to operate within a band of frequencies and the width of the conductive strip remains substantially constant along the length of the conductive strip and the length of the conductive strip is substantially equal to a half wavelength of a center frequency of the band of frequencies.
23. The REID system according to claim 21 , wherein the coupler is configured to operate within a band of frequencies and the width of the conductive strip varies along the length and defines a tapered profile and the length of the conductive strip is less than a half wavelength of a center frequency of the band of frequencies.
24. The REID system according to claim 23 , wherein the tapered profile is a modified bow-tie profile.
25. The REID system according to claim 23 , wherein the tapered profile is selected from the group consisting of an exponential profile and a Klopfenstein profile.
26. The REID system according to claim 15 further including a plurality of couplers for coupling with the at least one targeted transponder in the transponder encoding region.